[elbucko]

So, was this an "evolutionary" process or did horses always pass immunity on in this manner?

I don't know because the equines that never developed this ability to evolve adaptability to local infectious agents did not survive when they were exposed to new infectious agents, bacteria or virus. When they died the scavengers ate the carcass.

The argument many creationists advance is the rhetorical question of where are the "extinct" inferior species. That's just it. they're gone.

[ApesForEvolution]

How convenient. I've discovered that if God isn't bigger than my brain, then He can't be God. It is fun though to examine how His Word supports the scientific bases of the reality we live in during this dispensation...